1. Circles seem to breed if you're not careful. Less is more. And less which get used in a purposeful way is even more than that!
2. Number your circles so that they sort in the order you want. By default, system created circles (i.e. Friends, Acquaintances, Following) sort above your numbered circles if you don't give them a number... so number those too!
3. The only formatting you can apply to text is bold, italic and strikethrough (thanks AJ Cann for that!) - to do that, just pop a couple of asterisks around the word you want emboldened... *bold* = bold ... for italic it's... _italic_ = italic and strikethrough is... -strikethrough- =
4. Control your email notifications by going to Account settings > Google+ then adjust the notifications to suit.
5. Post from Google+ to Facebook by going to their mobile site, copying your unique Upload via email address, go back to Google+ create a circle and call it something like 'Facebook update', then paste in the email address you just copied to the 'add a new person' field. Then, when you want to send something to Facebook, just share it with your Facebook update circle.
6. To quickly see all the people you've added to a circle, go to circles, right click and select 'View circle in tab'...
7. ... once they're in a tab, you can select the ones you want to remove or drag to another circle (or even block en masse)
9. If you want to see how your profile looks to others, there's a little 'view profile as' link on your profile page where you can see what people can view from within Google+ and what everyone else sees .
10. Sparks are good! Too lazy to sift through the 101 RSS feeds you enthusiastically subscribed to? Just type in a search term and it'll pull up related content. If it looks like something you want to see in the longer term, then pin the interest and you'll see it on your main Google+ page.
11. Mute annoying posts by using the dropdown arrow next to the post and selecting mute (or block the individual if you really want to!)
12. If you've uploaded more than one profile picture, you can toggle between pictures on your profile page, just by clicking on your picture.
13. Don't forget to explore the privacy options - make sure you have your profile under control... reveal the information you want to reveal and no more! Share the posts you want with the people you want... and control whether or not they can comment / reshare. Make active choices with this stuff!
That's about it at the mo. It's obviously a system under development. It doesn't quite feel like a rival to Facebook to me. Or a Twitter replacement. Or a Skype replacement. It doesn't really feel like any one thing as yet. It feels like a shell for other things. But, unlike Google Wave which was chaotic and frenetic, it has an order which feels more able to be useful.
... though I still have the nagging feeling that I'm being sucked into the big Google Machine with every click...